How to do it
If you don't want to paint an entire ceramic tile surface, color the grout instead. Colorants made specifically for grout can dramatically alter the color scheme of the floor. First chip out any loose grout with a hammer and cold chisel and vacuum the loose dust. Patch the repaired spots with the same grout as the original, finish it with a striking tool, and let cure. Mix up the colorant and apply it to the grout with a narrow brush. Repeat the application to make the color darker.